1. Field of the Invention
The present invention relates to a light modulating device in which a plane-shaped light beam is incident and its transmittance is changed to perform exposure and an exposure apparatus using the same, more specifically relates to the optimum device for a system performing on-demand direct photolithography, particularly it is preferable for the system, which applies projection exposure by using the two-dimensional light modulating device, such as an image forming apparatus and a projector.
2. Description of the Related Art
In recent years, the exposure apparatus for performing the on-demand direct photolithography of a pattern image onto a photosensitive material without using a photomask is expected during a photolithographic process in a pattern formation of an electronic circuit for a circuit board or a display device or the like. Techniques of the related art will be described below showing examples.
As shown in FIG. 19, in WO98/47042 (Japanese Patent Application National Publication No. 2001-521672), a transmission two-dimensional light modulating device 484 is irradiated with a plane-shaped light beam emitted from a light source for illumination 482. The two-dimensional light modulating device 484 controls transmittance of the incident light in each light modulating element according to an image signal, projects the outgoing light on an exposure surface 486, and exposes the exposure surface 486. A liquid crystal device, PLZT, an electro-mechanically driven light modulating device, and the like are used as the above-described transmission two-dimensional light modulating device 484. A reflection type can be also used as the two-dimensional light modulating device, an electro-mechanically driven deflection mirror array device, which is known as a DMD device, can also be used. In this case (not shown), the substantially parallel light emitted from the light source for illumination is incident to the reflection two-dimensional light modulating device, the two-dimensional light modulating device controls a reflection angle of the incident light in each light modulating element according to the image signal, projects the outgoing light on the exposure surface, and exposes the exposure surface. In an embodiment of the related art (Japanese Patent Application National Publication No. 2001-521672), an imaging optical system including a microlens array is provided as a projection exposing system.
When maskless direct photolithographic exposure for the photolithography is considered as an application of the exposure apparatus in the pattern formation of the electronic circuit for the circuit board or the display device, practically since the number of light modulating elements in the two-dimensional light modulating device is smaller than the required number of light modulating elements, the necessary light modulating elements are exposed by scanning an exposure optical system or an object to be exposed.
FIGS. 20A, 20B, 21A, and 21B show features of the related art disclosed in Japanese Patent Application National Publication No. 2001-521672. FIG. 20A shows an arranging direction of the two-dimensional light modulating device in the usual exposure surface, and an example in the case that a column of the two-dimensional light modulating device and a scanning direction are arranged in parallel. In this case, when the exposure scanning is performed along the scanning direction, the light modulating elements are overlapped in the column direction, and resolution perpendicular to the scanning direction is restricted by a pitch of the light modulating element in a row direction of the two-dimensional light modulating device. On the other hand, as shown in FIG. 20B, when the column of the two-dimensional light modulating device is arranged to be oblique relative to the scanning direction, the resolution perpendicular to the scanning direction on the exposure surface is significantly increased by the pitch of the light modulating element in the column direction and an oblique angle. However, as shown in FIG. 20B, when a size of the light modulating element is large, the practical useful resolution is not obtained because spots of the light modulating elements are overlapped on the exposure surface.
In order to make the most of the above-described effect, as shown in FIG. 21A, an opening whose area is smaller than that of the light modulating element is provided for the light modulating element of the two-dimensional light modulating device in the related art. Accordingly, as shown in FIG. 21B, when the column of the two-dimensional light modulating device is arranged to be oblique relative to the scanning direction, the effect in which the resolution perpendicular to the scanning direction on the exposure surface is substantially increased is obtained.
By the way, in the above-described related art, though there is the description in which the opening is provided in the light modulating element of the two-dimensional light modulating device, no concrete structure is shown. Supposing that the structure of the related art is the structure which is usually thought, a problem will be described below.
For example, FIG. 22 is an explanatory view in the case that a shielding portion is simply formed in the light modulating element of the two-dimensional light modulating device to provide the opening. The liquid crystal device is shown as the transmission two-dimensional light modulating device. Though the details are omitted, a first transparent substrate 504 is bonded to a second transparent substrate 514 via a spacer 506. Liquid crystal 508 is sealed between these substrates. The light modulating element is usually determined by a light-modulating element electrode (not shown) arranged in the form of a matrix. At this point, since the above-described opening 510 is provided, when a shielding film 512 is formed on the first transparent substrate 504, the incident light is shielded in the region except the opening 510, and the problem in which usability of the light is decreased occurs (even if the shielding film 512 is formed on the second transparent substrate 514, the same problem occurs).
When a liquid crystal device is used as the transmission two-dimensional light modulating device, disadvantage is generated in high-speed response.
When an electro-optic crystal such as PLZT is used as the two-dimensional light modulating device, while two-dimensionability or low-voltage drive became difficult, there is a limit to a kind of light source, and it is impossible to optionally select the kind of light source in the wide range from UV light to infrared light.
Further, when a reflection DMD device is used as the two-dimensional light modulating device, an optical system became complicated and it is disadvantageous that manufacturing cost is increased.